Control means for liquid fuel injection pumps



June 1, 1954 F M, EVANS 2,679,836

CONTROL MEANS FOR LIQUID FUEL INJECTION PUMPS Filed OCT. 19, 1951 v j k I d Y,

Patented June 1, 1954 NITED STATES ENT OFFICE CONTROL MEANS FOR LIQUID FUEL INJECTION PUMPS Application October 19, 1951, Serial No. 252,088

Claims priority, application Great Britain November 8, 1950 3 Claims.

This invention relates to variable-delivery liquid fuel injection pumps for use with supercharged internal combustion engines.

lhe invention comprises the combination with the output control means of the pump, of means responsive to boost-pressure for actuating the said control means.

In particular the invention comprises the combination with the output control means of the pump, of an air-actuated servo-mechanism for actuating the said control means, and a mechanism responsive to boost-pressure for controlling the servo-mechanism.

In the accompanying drawings:

Figures 1 and 2 are sectional views illustrating diagrammatically two embodiments of the invention.

A known form of liquid fuel pump comprises a plurality of reciprocatory plungers. For varying the output of the pump, the plungers are adapted to control spill passages in the pump, the control being effected by rotation of the plungers about their axes under the action of a slidable rack bar connected through pinions to the plungers.

In the accompanying drawings, one end of this bar is indicated by a.

In one manner of applying the present invention to such a pump as shown in Figure 1, the slidable bar a may be loaded by a spring (not shown) which can move one end of the bar into contact with a stop I) which determines the position of maximum delivery. Adjacent to this end of the bar and stop, is pivotally mounted a lever c which is loaded by a spring d, the lever being supported at one end on a spindle e, and being provided with an adjustable abutment f in contact with the adjacent end of the bar a. The spring cl is so arranged that it tends to move the lever away from the bar. Alternatively, the lever may be connected to the bar, in which case the spring 01 serves also to move the bar towards the stop.

In association with the free end of the lever c is arranged a servo-mechanism. This comprises a cylinder g and a hollow piston h slidable in the cylinder, one end of the latter being open (directly or indirectly) to the atmosphere as through an orifice i. Coaxially with the end of the cylinder remote from the lever, is arranged a smaller cyl inder 7' containing a piston k (herein termed the boost-responsive piston), the piston being loaded by a spring m, and one end of the cylinder being in communication with a passage n leading to a pipe connection for admitting air to the cylinder from the super-charger.

From the end of the boost-responsive piston is extends a hollow piston rod 0 which passes through the end wall 11 of the part of the cylinder to which boost-air is admitted, and the outer end of this rod enters a central hole q in the adjacent end of the servo-piston h where it performs the function of a valve for controlling air flow through the said hole. Air is admitted to the servo-cylinder g from the cylinder 7' containing the boost-responsive piston k by way of a restricted orifice T, which may be arranged as shown, or it may be provided by a small clearance in the end wall of the cylinder through which the piston rod extends.

The mode of action is as follows:

When the engine is at rest one end of the pump control bar a is in contact with the maximum-delivery stop b, and the spring d acting on the lever 0 holds the servo-piston h in a position adjacent to one end of its cylinder. Also the spring m acting on the boost-responsive piston holds the latter in a position in which the piston rod 0 extends to its full extent through the hole q in the servo-piston. When the engine is in motion, air from the supercharger moves the boost-responsive piston it against the action of its spring m, and the air passing through the restricted orifice r to the servo-cylinder moves the servo-piston h in the opposite direction against the action of the lever spring d, and causes the lever to move the pump control bar it away from its stop to a position corresponding to the pressure acting on the servo-piston, so reducing the pump output to an appropriate amount. When the mechanism is in a state of balance corresponding to a particular boost-pressure, the outer end of the piston rod 0 lies within the hole q in the servo-piston in such a position that it allows a small amount of air to pass from the servo-cylinder to atmosphere through perforations in the end of the piston against which the lever c abuts. The effect of an increase of boost-pressure is to allow more air to pass from the servo-cylinder g past the piston h, and the consequent fall of air pressure acting on the servo-piston allows the spring at acting on the lever c to move the servo-piston until it overtakes the piston rod 0 and restricts the hole in the piston. A new steady state is thereby reached, and in this movement of the lever, the control bar under the action of its spring or otherwise, moves the latter towards its end stop for effecting a corresponding increase in the pump output.

When the pump has combined with it a maximum-speed governor, this comes into operation on attainment of a predetermined speed for moving the control bar a away from its end stop for reducing the pump output.

In another embodiment of the invention as shown in Figure 2, the hole q in the servo-piston h is occupied by a spring loaded poppet valve s. In this example the lever is pivoted between its ends by the spindle e. One end of the lever carries the adjustable abutment f and the other end bears against the servo-piston h. The spring 711. acting on the boost-responsive piston is is arranged to move the latter in the opposite direction to that in the example shown in Figure 1, and air from the supercharger is admitted through the passage n to the end of the cylinder remote from that through which the rod extends. Also air is conveyed to the remote end of the servo-cylinder g by an extension of the passage n which includes a restricted orifice 1'. Further, instead of the rod 0 being formed on or secured to the boost-responsive piston, it consists of a separately formed thrust rod, one end being in contact with this piston is and the other end being adapted to open the valve s in the servo-piston h.

The mode of action is essentially similar to that of the first described example. When the mechanism is in a steady state, the valve s is moved to or near its closed position by a spring t and is in light contact with the thrust rod 0. With increase of boost-pressure, the boost-responsive piston 7c is moved against the action of its spring 111. in the direction for opening the valve s and so releasing the air-pressure acting on the servo-piston h, air being then able to escape from the cylinder 9 through perforations in one end of the piston 71. and through the hole q controlled by the valve s. The lever 0 under the action of the spring 01 now moves the servo-piston it until the valve is re-closed. Meanwhile the spring acting on the control bar a moves the latter in the direction for effecting a corresponding increase of fuel supply.

The invention is not, however, restricted to the examples above described, as it may be embodied in other forms for enabling the control means of the pump to be automatically movable in response to variations of boost-pressure.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Means for controlling the output of a variable-delivery liquid fuel injection pump for use with a super-charged internal combustion engine, comprising in combination a movable output control means for the pump, a spring-loaded lever constituting a variable position stop for said output control means, a first cylinder, a hollow piston provided with an air-flow aperture and slidable in said cylinder under boost air pressure to vary the position of said lever which has one end situated in the path of and bearing against said hollow piston, said cylinder being provided at one end with an inlet for boost air, a second cylinder arranged coaxially with said first cylinder, a spring-loaded piston slidable in said second cylinder under boost air pressure, said second cylinder being provided at one end with an inlet for boost air, and an axially movable rod situated between the two pistons and operable by said spring-loaded piston to control the flow through said aperture of boost air acting on said hollow piston.

2. Means as claimed in claim 1, in which said rod is rigid with said spring-loaded piston, and cooperates with said aperture to control air flow therethrough.

3. Means as claimed in claim 1, and having a spring-loaded valve for controlling air flow through said aperture, said valve being operable by said rod.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,374,411 Camner Apr. 24, 1945 FOREIGN PATENTS Number Country Date 52,143 France 1943 (Addition to No. 877,659) 825,791 France Mar. 14, 1938 844,885 France 1939 504,170 Great Britain Apr. 20, 1939 204,344 Switzerland July 17, 1939 

